The sputtering process is used in various industrial manufacturing processes, such as in semiconductor integrated circuits and magnetic media, to create sacrificial and protective coatings on various parts of the sputtering machine. These protective coatings serve to protect and extend the service life of some critical machine parts, such as those of sputtering system. The machine parts can be, for example, shields, wafer carriers, and disk carriers. Further, the protective coatings can also be produced by various methods including electroplating and thermal coating methods, such as twin wire arc spray, flame spray, and plasma spray.
During the sputtering process, one of the main problems is the generation of particles caused by de-lamination and flaking of the coated surfaces. Such flaking and de-lamination generate defects on the surface of the substrates, such as Silicon wafers and magnetic disks.
Aluminium, produced by thermal spray methods, is one of the most common protective coatings deposited on the surface of the sputtering machine parts. Although Aluminium generally has a beneficiary effect, the physical properties of the Aluminium protective coating and sputtered material cause de-lamination and flaking, which further result in particles with the detrimental effect as described above.
Efforts are made to reduce the detrimental effects of the sputtered Aluminium material. The physical properties of the Aluminium material are modified by adding another element, i.e., Silicon (‘Si’), in various amounts to create a better consistency of the physical properties. Specifically, consistent with the thermal properties, between the Aluminium-Silicon protective coating, the sputtered material, and the part substrate, in order to reduce the de-lamination and flaking that result in generation of particles.
Attempts are made to create the protective coating by twin wire arc spray using Aluminium-Silicon wires of various compositions of Si, such as Al-6% Si. The results were not good enough. As well known, the thermal spray coating creates a columnar porous structure. However, in the case of the 6% Si, the structure of the porous frame was not rigid enough, basically due to the strength of the material, which further caused breakage and collapse of the coating. Thereby, resulting in flaking.